Supposing, however, that the case is none of these, the very first prognostic consideration is that of age.
Of the neuralgias of youth, the majority either disappear altogether after a first attack, or recur a certain number of times during some years, the neuralgic tendency either disappearing or becoming greatly mitigated when the process of bodily consolidation is over. In another group the neuralgic tendency is never lost, but the form of the attacks changes, and there is far less spontaneity in the manner of their production. It is exceedingly common to see delicate boys and girls between puberty and the age of eighteen or twenty, attacked with typical migraine, which recurs regularly every three or four weeks for perhaps two or three years, then ceases to occur at regular periods, then loses the tendency to stomach complication; and, by the age of twenty-five or somewhat later, has left, as its only relic, a tendency to attacks of ophthalmic neuralgia, which come on when the patient is excessively fatigued, or encounters the close air of a theatre, or undergoes an unusual strain of mental excitement or anxiety, etc.; but which never come on without some such special provocation. So, again, there is a variety of sciatica which belongs mainly to the period between puberty and the twenty-fifth to thirtieth year, and which seems really to belong, pathologically, to the age of unsettled and irregular sexual function, the tendency to it usually disappearing after the patient has settled down happily in married life. Ovarian and mammary neuralgia have very commonly a similar history.
On the other extreme we find the neuralgias of the period of bodily decay: these are of very bad prognosis. A neuralgia which first develops itself after the arteries and capillaries have begun to change decidedly in the direction of atheroma is extremely likely, even if apparently cured for a time, to recur again and again, with ever-increasing severity, and to haunt the patient for the remainder of his days. It therefore becomes exceedingly important, in a prognostic point of view, to assure ourselves as soon as possible whether this arterial degeneration has decidedly commenced; and for this purpose I am in the habit of insisting to pupils on the great importance of sphygmographic examination for all neuralgic patients who have passed the middle age. Where we get the evidence which is furnished by the formation of a distinctly square-headed radial pulse-curve, even though there be no palpable cord-like rigidity of superficial arteries, we are bound to be exceedingly cautious of giving a favorable prognosis.
In women the period of involution of the sexual apparatus forms a crisis which, in regard to neuralgias, is of great prognostic importance. On the one hand, if the general vital status be good, and the arterial system fairly unimpaired, we may look to the completion of the process of involution as a probable time of deliverance from neuralgic troubles that have hitherto beset a woman; we know that she will probably suffer a temporary aggravation of her pains, but we hope to see her lose them altogether. On the other hand, if it should happen that she enters on the period of sexual involution with her general nutrition considerably impaired and her arterial system decidedly invaded by atheroma, it is only too likely that neuralgias recurring now, or attacking her for the first time, will assume the worst and least manageable type.
Of almost or quite equal importance with the question of the physiological age of the patient is that of his personal and family history with regard to the tendency to neuralgia and to other severe neuroses. Upon this subject I have dwelt so very fully in other parts of this work, that it is merely necessary here to repeat, that the balance of chances is most heavily swayed to the bad side by all evidence tending to prove congenital neurotic tendencies in the patient and vice versa.
Of prognostic hints that are to be gathered from our knowledge of the immediate causes of the attack, there are none so valuable as those which we gather from the detection of a malarial or a syphilitic factor in the production of the malady. In the former case, we hope to cure the patient either with quinine or arsenic, with almost magical certainty and rapidity; in the latter, we expect an almost equally brilliant result from iodide of potassium.
The particular nerve in which the neuralgia is seated does not so decidedly influence the prognosis, according to my experience, as is stated by some authors; nevertheless, there are differences of this kind. For instance, sciatica, though by no means so frequently a mild and trifling complaint as Eulenburg would make it to be, is certainly, on the whole, more curable than the trigeminal neuralgias taken as a group. I, however, cannot share Eulenburg's opinion as to the rarity of a central cause for sciatica, nor his consequent explanation of its more frequent curability; the latter I explain by the fact that it is possible far more completely to remove the concomitant causes in sciatica than in trigeminal neuralgia. By simply keeping a sciatic patient in the prone posture, shielded from cold and from pressure on the nerve, we have it in our power to remove nearly all peripheral sources of irritation; but in trigeminal neuralgia there are many influences, particularly psychical ones, which cannot be shut out, and which will continue to act with disastrous effect in many cases. With all this, however, we see a sufficiently large number of incurable sciaticas, on the one hand, and of severe trigeminal neuralgia cured on the other. It is only the genuine epileptiform tic, occurring in subjects whose arterial system is an advanced stage of degeneration, that stands out clearly and unmistakably pre-eminent among neuralgias for rebelliousness to treatment of every kind.